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Groups > comp.arch.embedded > #28296

Re: RS485 over optical fiber cable

From pozz <pozzugno@gmail.com>
Newsgroups comp.arch.embedded
Subject Re: RS485 over optical fiber cable
Date 2018-10-31 12:41 +0100
Organization A noiseless patient Spider
Message-ID <prc4e3$chj$1@dont-email.me> (permalink)
References <pr9o50$m9b$1@dont-email.me> <7686c6c0-7f2a-49b9-94d2-da49b7ab32ef@googlegroups.com>

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Il 30/10/2018 15:26, raimond.dragomir@gmail.com ha scritto:
> marți, 30 octombrie 2018, 16:00:06 UTC+2, pozz a scris:
>> I'd like to replace an electrical cable with a fiber cable, mainly for
>> electromagnetic noise immunity and long distance (I need to reach 500m).
>> The bitrate will be very low: 9600bps is ok.
>> I need to keep the cost low as possible.
>>
>> I never used fiber cables before. In similar applications I used RS485
>> transceivers connected to the UART peripheral of an MCU.
>>
>> I think I need a fiber optic cable transceiver, but I don't know what to
>> search and how to interconnect with an MCU.
>>
>> Any help?
> 
> 9600bps, 500m, RS485.
> It's all you need.
> Probably you also need galvanic isolation. Use optocouplers.
> Use three wires, A,B,C. C is the common ground for ONLY RS485 communication, isolated on ALL ends.

Do you use CAT5E cable and connect A and B to a couple?
What's about termination resistor?  In the past I used very small RS485 
links (under 100m) with low bitrate (maximum 38400bps), so I never used 
termination resistor.

I think I need it for 500m link.  Is the usual 120R ok?


> I also use small 5V:5V DC/DC converters on all nodes to isolate the RS485 part.


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Thread

RS485 over optical fiber cable pozz <pozzugno@gmail.com> - 2018-10-30 15:00 +0100
  Re: RS485 over optical fiber cable raimond.dragomir@gmail.com - 2018-10-30 07:26 -0700
    Re: RS485 over optical fiber cable pozz <pozzugno@gmail.com> - 2018-10-31 12:41 +0100
      Re: RS485 over optical fiber cable raimond.dragomir@gmail.com - 2018-10-31 05:55 -0700
      Re: RS485 over optical fiber cable Grant Edwards <invalid@invalid.invalid> - 2018-10-31 14:03 +0000
        Re: RS485 over optical fiber cable John Speth <johnspeth@yahoo.com> - 2018-10-31 09:35 -0700
          Re: RS485 over optical fiber cable Grant Edwards <invalid@invalid.invalid> - 2018-10-31 16:48 +0000
            Re: RS485 over optical fiber cable pozz <pozzugno@gmail.com> - 2018-11-02 14:44 +0100
              Re: RS485 over optical fiber cable Richard Damon <Richard@Damon-Family.org> - 2018-11-02 11:00 -0400
                Re: RS485 over optical fiber cable upsidedown@downunder.com - 2018-11-02 20:42 +0200
              Re: RS485 over optical fiber cable raimond.dragomir@gmail.com - 2018-11-02 08:18 -0700
              Re: RS485 over optical fiber cable Mike Perkins <spam@spam.com> - 2018-11-02 15:22 +0000
                Re: RS485 over optical fiber cable Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-11-02 21:31 +0200
                Re: RS485 over optical fiber cable Mike Perkins <spam@spam.com> - 2018-11-02 20:12 +0000
                Re: RS485 over optical fiber cable Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2018-11-02 23:57 +0100
                Re: RS485 over optical fiber cable upsidedown@downunder.com - 2018-11-03 01:18 +0200
                Re: RS485 over optical fiber cable Mike Perkins <spam@spam.com> - 2018-11-03 19:05 +0000
                Re: RS485 over optical fiber cable Richard Damon <Richard@Damon-Family.org> - 2018-11-03 17:36 -0400
                Re: RS485 over optical fiber cable gnuarm.deletethisbit@gmail.com - 2018-11-03 19:49 -0700
                Re: RS485 over optical fiber cable upsidedown@downunder.com - 2018-11-04 07:50 +0200
                Re: RS485 over optical fiber cable pozz <pozzugno@gmail.com> - 2018-11-05 09:40 +0100
                Re: RS485 over optical fiber cable Richard Damon <Richard@Damon-Family.org> - 2018-11-05 06:45 -0500
                Re: RS485 over optical fiber cable Rob Gaddi <rgaddi@highlandtechnology.invalid> - 2018-11-05 09:12 -0800
              Re: RS485 over optical fiber cable Grant Edwards <invalid@invalid.invalid> - 2018-11-02 18:21 +0000
                Re: RS485 over optical fiber cable upsidedown@downunder.com - 2018-11-03 00:02 +0200
          Re: RS485 over optical fiber cable pozz <pozzugno@gmail.com> - 2018-11-02 14:36 +0100
    Re: RS485 over optical fiber cable "Mat Nieuwenhoven" <mnieuw@zap.a2000.nl> - 2018-10-31 16:32 +0100
    Re: RS485 over optical fiber cable upsidedown@downunder.com - 2018-10-31 22:41 +0200
  Re: RS485 over optical fiber cable Chris <c@b.a> - 2018-10-31 12:16 +1100
    Re: RS485 over optical fiber cable upsidedown@downunder.com - 2018-11-02 06:52 +0200
  Re: RS485 over optical fiber cable Robert Wessel <robertwessel2@yahoo.com> - 2018-10-31 09:11 -0500
  Re: RS485 over optical fiber cable peter jakacki <peterjakacki@gmail.com> - 2018-11-12 19:57 -0800
    Re: RS485 over optical fiber cable upsidedown@downunder.com - 2018-11-13 08:09 +0200

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